Former Vice President Joseph R. Biden Jr. says his son never reached out to him about a prosecutor in Ukraine who was ultimately dismissed, after he had reportedly been eyeing an energy company with ties to Hunter Biden.

“All the reporting has indicated that there is not a single, solitary thing was inappropriate about what my son did. He never once talked to me never once talked to anybody in the administration,” the former vice president and 2020 presidential candidate told WMUR, a New Hampshire affiliate.

The New York Times reported earlier this month that on a trip to Kiev in March 2016, Mr. Biden had threatened to withhold $1 billion in U.S. loan guarantees if Ukraine’s leaders didn’t dismiss the prosecutor, who had reportedly had his sights on an energy company that was owned by a Ukrainian oligarch. Hunter Biden was on the board of the company at the time.

The paper also first reported that former New York City Mayor Rudolph W. Giuliani, one of President Trump’s private lawyers, had been planning a trip to Ukraine to urge leaders to pursue inquiries that could be beneficial to Mr. Trump’s reelection campaign.

But Mr. Giuliani said late last week that he wouldn’t make the trip, saying he suspected he was walking into a group of people who were enemies of the president.

“It’s sort of Giuliani’s style [and] this administration,” Mr. Biden said. “It is inappropriate. Unrelated to me, it’s just inappropriate to send your lawyer to a foreign government to try to get them to do something that has no bearing except to ... try to embarrass.”

Mr. Trump’s official team had tried to distance itself from Mr. Giuliani’s efforts.